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Urethane casting is a versatile process for fabricating plastic and rubber parts at low to medium production volumes. Similar to injection molding, urethane casting uses a two-part mold where the two halves combine to create a void that the urethane is poured into until a cured part is formed. The process produces parts with colors, textures, mechanical properties and surface finishes comparable to those made with injection molding.
Why use cast urethane
If your part has a fairly simple geometry that requires a silicon or rubber material, then cast urethane is an ideal solution. Cast urethane does not pose the same startup costs as injection molding because silicone molds are relatively economical, which makes the process suitable for low volume production.
We recommend urethane casting if you need:
- Parts with a rubbery consistency and consistent mechanical properties
- An array of material types (e.g., rigid, flexible, durable or clear)
- Low volume production at an economical cost
Cast urethane specifically deals with ABS- and PE-like plastics, rubbers, silicon and elastomers. Although cast urethane has a limited material library compared to injection molding, it still offers materials that exhibit various hardnesses and looks; some even have MR, UL and FDA certifications.
How cast urethane works
- A master pattern is printed with Stereolithography (SLA) and subsequently encased in liquid silicon to create the mold
- After it’s cured, the mold is cut in half and the pattern is removed
- During the molding process, the cavity is filled with the chosen material
- The material is then left to cure, after which the final part is removed from the mold
Urethane casting is commonly used to manufacture parts with joints or overlapping features.
Logos with raised or recessed letters can be created with urethane casting and assembled onto customer-facing products.
Considerations for cast urethane
The success of cast urethane depends on the quality of the master mold, casting material and part geometry. All three influence the shrinkage rate, which needs to be at or under 0.15%.
You’ll also need to consider design for manufacturing (DFM) to ensure successful production runs. Think about:
- Eradicating growth lines that appear in internal features with custom finishes
- Printing larger products separately and assembling them together during post processing
- Having a minimum wall thickness of 1 mm so your part is supported
- Incorporating a draft into the mold design to increase its lifespan
When to consider additive
Cast urethane works well if your spec identifies relatively simple parts to be made with specific plastics or rubbers at low volumes. However, if your spec identifies complex parts, then additive might be more economical, especially if a comparable plastic material is available.
For example, if you’re iteratively designing a complex part with an ABS-like plastic, then Carbon digital light synthesis (DLS) might be a good fit because the process quickly produces parts in low volumes and accommodates the specced plastics.
Discuss your manufacturing needs with our team by requesting a quote to see if cast urethane works for your application.
- Low cost for small production runs
- Consistent mechanical properties
- Fast production once mold is created
- Capable of producing rubbery parts
- Requires a mold made with a different process
- Higher cost for large runs compared to injection molding
ABS-Like, PE Like, Elastomers (25A – 90A), PP-Like, Lexan-Like, High Strength, 94V0 ABS-LikeGet A Quote